Travel Medicine Centre

Yellow Fever &
Diseases Subject to InternationalHealth Regulations

Yellow Fever

Yellow fever inoculation is recommended to all travelers in transit or going to the yellow fever endemic zones
of Africa and Central and South America. In many cases it is required. There are no yellow fever endemic areas
in Asia and travelers to these areas do not require yellow fever unless they go through Africa or South
America. Yellow fever vaccine must be administered in a WHO approved vaccination center. Yellow fever is a
live vaccine grown in eggs. It should not be given to those with cancer or to those with decreased immunity.
It should not be given during pregnancy unless the risk of yellow fever is very high. It should be avoided in
patients with a known allergy to eggs. Intradermal skin testing can be done to determine sensitivity in these
cases. The vaccine is given to those over 6 to 9 months of age and after a single dose the certificate is
valid for 10 years starting 10 days after administration.

As of June 2016 yellow fever vaccination certificates will be valid for life. Those
travelers with contraindications to use or infants under 9 months of age should be given a certificate of
exemption.

Yellow Fever Endemic zones - Africa (WHO CDC)

Yellow Fever Endemic zones - Americas (WHO CDC)

More info onYellow Fever Vaccine from CDC

Yellow fever is preventable by a relatively safe, effective vaccine. All yellow fever vaccines currently
manufactured are live attenuated viral vaccines.

YF-VAX, the only yellow fever vaccine approved for use in the United States and Canada, is manufactured by
sanofi pasteur. Studies comparing the reactogenicity and immunogenicity of various yellow fever vaccines,
including those manufactured outside of the United States, suggest that there is no significant difference in
the reactogenicity or immune response generated by the various vaccines. Thus, individuals who receive yellow
fever vaccines in other countries should be considered protected against yellow fever.

Recommendations for the Use of Yellow Fever Vaccine for Travelers

Persons aged ≥9 months of age who are traveling to or living in areas with risk of yellow fever transmission
in South America and Africa should be vaccinated. In addition, some countries require proof of yellow fever
vaccination for entry. See the following section in this chapter (Yellow Fever Vaccine Requirements and
Recommendations, by Country) for more detailed information on the requirements and recommendations for yellow
fever vaccination for specific countries.

Reported events typically include low-grade fever, headache, and myalgias that begin within days after
vaccination and last 5–10 days.

Approximately 1% of vaccinees temporarily curtail their regular activities because of these reactions.

Severe Adverse Events

Hypersensitivity

Immediate hypersensitivity reactions, characterized by rash, urticaria, or asthma or a combination of these,
are uncommon. Anaphylaxis following yellow fever vaccine is reported to occur at a rate of 1.8 cases per
100,000 doses administered.

Yellow Fever Vaccine-Associated Neurologic Disease (YEL-AND)

YEL-AND represents a conglomerate of different clinical syndromes, including meningoencephalitis, Guillain–Barré
syndrome (GBS), acute disseminated encephalomyelitis (ADEM), bulbar palsy, and Bell’s palsy. Historically,
YEL-AND was seen primarily among infants as encephalitis, but more recent reports have been among persons of
all ages. The onset of illness for documented cases ranges 3–28 days after vaccination, and almost all
cases were in first-time vaccine recipients. • YEL-AND is rarely fatal. The incidence of YEL-AND in
the United States is 0.8 per 100,000 doses administered. The rate is higher in persons ≥60 years of age, with
a rate of 1.6 per 100,000 doses in persons 60–69 years of age and 2.3 per 100,000 doses in persons ≥70 years
of age.

Yellow Fever Vaccine-Associated Viscerotropic Disease (YEL-AVD)

YEL-AVD is a severe illness similar to wild-type disease, with vaccine virus proliferating in multiple organs
and often leading to multisystem organ failure and death.

Since the initial cases of YEL-AVD were published in 2001, more than 40 confirmed and suspected cases have
been reported throughout the world.

The onset of illness for YEL-AVD cases averaged 3.5 days (range: 1–8 days) after vaccination. YEL-AVD appears
to occur after the first dose of yellow fever vaccine rather than with booster doses.

The case–fatality ratio for reported YEL-AVD cases is 53%.

The incidence of YEL-AVD in the United States is 0.4 cases per 100,000 doses of vaccine administered. The rate
is higher for persons ≥60 years of age, with a rate of 1 per 100,000 doses in persons 60–69 years of age and
2.3 per 100,000 doses in persons aged ≥70 years of age.

Cholera

The existing injectable cholera vaccines do not prevent the development of the carrier state or affect the
severity of the disease. They do not prevent the introduction of cholera into a country or interrupt
transmission. The risk to travelers is low. The International Health Regulations abolished the requirement of
a vaccination certificate in June 1973. No country should require a certificate from travelers arriving from
Canada. We provide an exemption certificate to each traveler which is sufficient to avoid inconvenience. A new
oral cholera vaccine is available in some countries and is relatively effective for those few travellers
at high risk.

Dukoral

There is a new oral Cholera/Traveller's diarrhea vaccine available. Some travellers may want this to
prevent cases of enterotoxigenic E Coli infections, a common cause of severe travellers diarrhea. A few such
as aid workers or those going to very remote areas with cholera outbreaks may want it to prevent cholera. Cost
$40 per dose 2 doses required (plus boosters for frequent travellers).
Health Canada/CATMAT does NOT recommend this vacine to
prevent travellers diarrhea

Smallpox

Effective January 1982, smallpox was eliminated as a quarantinable disease. No country requires a vaccination
certificate and distribution of the vaccine for civilian use was discontinued in May 1983. The last reported
case was 1977.